For Clinical Purposes,the Most Accurate Definition of Preterm and Postterm

For clinical purposes,the most accurate definition of preterm and postterm infants is defined as what?

A) Preterm: Before 34 weeks of gestation if the infant is appropriate for gestational age (AGA) ;before 37 weeks if the infant is small for gestational age (SGA)
B) Postterm: After 40 weeks of gestation if the infant is large for gestational age (LGA) ;beyond 42 weeks if the infant is AGA
C) Preterm: Before 37 weeks of gestation and postterm beyond 42 weeks of gestation;no matter the size for gestational age at birth
D) Preterm: Before 38 to 40 weeks of gestation if the infant is SGA;postterm,beyond 40 to 42 weeks gestation if the infant is LGA